Clock synchronization in a communication network is a very important technology. Accuracy and timeliness of clock synchronization are directly related to quality of services of the whole network. There are two types of clock synchronization in the current communication network, i.e., time synchronization (also referred to as phase synchronization) and frequency synchronization. Time synchronization requires a same absolute time for individual points; and frequency synchronization keeps a same frequency for the individual points, which may be of any phase. Since clock equipment, in a process of tracking a clock source, only needs to regulate a frequency of a local clock signal to be the same as a frequency of the clock source without considering the phase, there is tracked phase accumulation.
In the conventional communication networks, there are relatively undiversified network types (for example, only one type of networks are usually included), the scale of a single network is not large, and the number of network nodes and the number of hops between the nodes are small, so that it is relatively easy to implement clock synchronization. For the current communication networks, the structures of thereof become increasingly complex, and there are more and more types of transport networks, for example, packet switched networks such as Internet Protocol (IP)/Multi-Protocol Label Switching (MPLS) and optical networks such as an Optical Transport Network (OTN) and a Synchronous Digital Hierarchy (SDH) network, the scale of a network is also rapidly extended, and a single network is developed from a single-type network to a multiple-type network, for example, a single network formed by hybrid networking of a Packet Transport Network (PTN) and an OTN. Moreover, a single network includes more and more network nodes, and topological relationships between the nodes gradually become complex.
Currently, in a multiple-type network, implementation of a cross-domain clock synchronization method relies on manual configuration. The conventional communication network which is relatively simple may be manually arranged to meet the network clock synchronization requirement. However, as the current network becomes increasingly complex, adoption of conventional manual configuration for implementing clock synchronization may cause tediousness of maintenance work. Moreover, the current network changes frequently, so that it is very difficult to implement clock synchronization of the current large network system by solely adopting the manual configuration manner.